As for conventional metal bellows, for example, formed metal bellows, U shaped bellows with U shaped peaks and valleys are known (hereinafter, referred to as “Conventional Art 1”. See Patent Documents 1 and 2, for example).
As for formed metal bellows, a bellows in which an average wave-top direction and an average wave-bottom direction are each inclined in opposite directions relative to the axis in order to increase the amplitude of the axial elasticity of the bellows is proposed (hereinafter, referred to as “Conventional Art 2”. See Patent Document 3, for example).
Further, as for metal bellows, an accumulator that includes a metal bellows formed in a cylindrical shape and capable of axial extension and contraction, a movable plate fixed to one end of the bellows, and an annular sealing member fixed to the undersurface of the movable plate, in which the annular sealing member can be seated on and separated from an upper base wall of a stay, and when seated, seals a working fluid (also referred to as a backup fluid) in a space formed between the bellows and the stay to prevent excessive contraction deformation of the bellows, is known (hereinafter, referred to as “Conventional Art 3”. See Patent Document 4, for example).